Why are story points about time

Unlike this cat, it is impossible to escape the wheels of time…

It doesn’t matter if you use T-shirt size or Story Points or something new, in the end, a year has 365 days, a week is 7 days and a day 24 hours.

The world runs on time. It is a currency we cannot exchange. A commodity we cannot buy more of.

So now that the grim part is out of the way, let me explain why I view SP’s like time. Let us start with the…


If you are using SCRUM, and you probably are, you know the concept of the SPRINT. There is also a high chance you have been using story points.

Sprints, if you don’t know already, are time-boxed windows of time. It starts with planning and ends with a review. Whenever one Sprint ends, a new one starts.
Depending on the needs of your stakeholders and how short your feedback loop, your sprint could go from 1 week to 4.

You can look at the sprint as a division of time on your calendar.
During the sprint, an increment of working software will be worked on and delivered in the end.
There are also other important features to the sprint, like Goals and Events, but for the sake of this argument let’s keep them away.

One way we estimate the amount of work we can pull into the sprint and deliver the increment is by using…

Story Points

Story points are the most used agile estimation metric.
One of the reasons why they are so famous is because they can be summed up (to extrapolate time). It is much harder to do if we are T-shirt sizing (S, M, L, XL).

It’s one of the hardest things to master and something gets in the way of what is important.

I’ve seen many teams get lost in the discussion of “the difference between a 2 and a 3”. You may disagree with me but I find this discussion very unproductive.
One thing I always do with my teams is to explain why it is unproductive and we should drop the 2’s and just focus on 1’s and 3’s.

The distance between 1,2,3 is only 1.
If that equates to around 1 or 2 days, who cares? We are doing a relative estimation, not a precise one.
By removing it, if its smaller than a 3 its a 1, if its bigger than a 3 its a 5. Much simpler.

So why do we estimate?

We do it to get a perception of the amount of work.
We do it to try and understand if the cost is bigger or smaller than the value that we expect to produce.

Over the years I have seen many explanations about what makes a good estimation. We need to include:

  • The amount of work to be done.
  • The complexity of the work.
  • The risk/uncertainty of what needs to happen.

Both the amount of work and complexity can be correlated to time.
Look at it like this:

  • Amount of work: Taking 100 coffees will take more time than taking only 1 coffee.
  • The complexity of the work: Taking 1 coffee will take less time than building a coffee machine.

Risk/Uncertainty is difficult to measure, so let us leave it for now and I will come back to it later.

It is Time

Now the interesting part.
If Story Points are time and, they are a relative measure of time, how does it work?

This scale is relative to a 2-week sprint. Your mileage may vary.
In working days :
1 = between 0 and 3
3 = between 2 and 5
5 = between 4 and 8
8 = between 6 and 10
i.e I expect this to take me between 2 to 3 days to deliver. Then this story is a “3”.

So where does the risk/uncertainty come into play?
You may have noticed that there is an overlap between the SP’s. This is where uncertainty and risk come into play.

  • How sure are you that you can complete this story in 2 days?
  • How risky is this story to do?
  • How familiar are you with what we need to do?

If either the uncertainty or risk is high, maybe you should go for a 5 instead of a 3.
Remember that the goal is to have a relative estimation, not an exact one.

The conclusion

Story points are about time. A range of Time.
We need to take into consideration both the risk and uncertainty of the feature.

During these years I have come to believe that there are better ways to measure team performance and do an estimation.
Better ways to provide more value to the teams and their discussions.
But… Let’s be honest. In the end, estimation or no estimation, the only thing that matters is : Are you delivering value or not?

This agile principle says it all: Working software is the only measure of progress.



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